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Microbes Help Obese People Metabolize their Food More Efficiently

2015-06-30

To continue with the theme of microbes in your intestines, I present an old study that demonstrates something of great importance to all those people who are told to diet, and there are a lot of them. This study is from 2006, and it merely confirms a common-sense hunch that explains why some people say they don’t eat anything and still gain weight; while other people can be observed to be gorging themselves on a regular basis, and such people are thin as rails.

The study, abstract available here, is entitled, “An obesity-associated gut microbiome with increased capacity for energy harvest” which explains pretty much everything. They found that two species of bacteria, Bacteroidetes and Firmicutes, endowed their hosts with the ability to harvest more energy from a normal diet. In addition, they were able to give these two species to mice that had previously been raised without any bacteria in their intestines; the newly infected, or really colonized, mice gained weight and increased total body fat. Finally, they showed that genetically obese mice seemed to mediate part of their weight gain through hosting these bacteria, whereas genetically normal weight mice did not harbor the same bacteria.

This information suggests that weight loss may be enhanced by eradicating these two populations of bacteria from the intestines. In fact, Huffington Post recommends avoiding sugars, which are Firmicutes favorite food, and eating more beans, which Bacteroidetes are accustomed to. According to that article, Bacteroidetes are actually better bacteria to have.

Inulin and oligofructose (both polysaccharides classed as fibers, with oligofructose having <= ten fructose molecules; both are plant storage carbohydrates) stimulate the growth of Bacteroidetes and reduce Firmicutes when fed to mice, in this study from 2013. Neither “fiber” is absorbed in the upper intestine, so in germ-free mice they provide no nutritional value. These foods also increase satiety hormones ghrelin and glucagon-like peptide 1, and reduce weight when fed to obese mice. This paper, presented at a conference in 1998, describes inulin as having a “neutral, clean flavor” and oligofructose as having a”sweet, pleasant flavor and is highly soluble” so it recommends them both as food additives. The paper describes how these foods are extracted from the chicory root and goes into some detail on production. The same paper, (in pdf form at this site) describes studies that show both foods to stimulate the growth of Bifidobacteria, which help synthesize B vitamins, stimulate the immune system, and inhibit or outcompete harmful bacteria.

These research studies and papers describe beneficial effects of the nutritional fibers inulin and oligofructose as food additives, with improved bacterial populations in the gut and possible stimulation of weight loss. It appears contradictory that some lean people can eat large amounts of food without gaining weight; yet the bacteria stimulated to grow in their intestines increase their energy utilization from, at least, certain polysaccharides.